Arrangements are well known by which fluid is dispensed from fluid containing reservoirs. One disadvantage of such arrangements is to prevent spilling or leakage of fluid prior to initiating use of the dispenser. For example, known hand soap dispensing systems provide rigid reservoirs containing liquid soap from which soap is to be dispensed. The reservoir is enclosed and rigid and, on dispensing liquid soap from the reservoir, a vacuum comes to be created in the reservoir. It is known to provide one-way valves which permit atmospheric air to enter the reservoir and permit the vacuum in the reservoir to be reduced. The one-way valves typically operate such that the one-way valve prevents air from entering the reservoir unless a vacuum is developed to a certain level below atmospheric pressure. However, known one-way valve mechanisms often permit flow of fluid outwardly therepast if, for example, the reservoir may become pressurized as by inadvertent squeezing or by inversion of the reservoir.
U.S. Pat. No. 5,676,277 to Ophardt which issued Oct. 14, 1997 discloses in FIG. 10 a known one-way valve structure in which a resilient flexible seal member is biased to close an air passageway such that on the development of vacuum within a reservoir, the seal member is deflected out of a position to close the air passageway and permits atmospheric air to enter the reservoir relieving the vacuum. Such flexible seal members suffer the disadvantage that they are subject to failure, do not always provide a suitable seal, and to be flexible must frequently be made from different materials than the remainder of the value structure. As well as insofar as a flexible seal member is to be maintained in contact with fluid from the reservoir, then difficulties may arise in respect of degradation of the flexible sealing member with time. As well, the flexible sealing member typically must experience some minimal level of vacuum in order to operate and such minimal level of vacuum can, in itself, at times present difficulty in dispensing fluid from the reservoir. Further, the flexible seal member can permit undesired fluid flow outwardly from the reservoir if the reservoir is pressurized.